As disclosed in the U.S. Pat. No. 4,529,183, a prior art vise capable of holding two work pieces simultaneously is provided With a threaded rod movable in the longitudinal direction, a movable jaw fastened with the rear end of the threaded rod, and another movable jaw fitted over the smooth portion of the threaded rod such that the movable jaw can be caused to move with the threaded rod along the longitudinal direction, and that the threaded rod can be caused to turn. In operation, one movable jaw can be caused to clamp one work piece first by rotating the threaded rod. Thereafter, another movable jaw is caused to hold another work piece by a reaction force of the first movable jaw, which actuates the movement of the threaded rod along with the second movable jaw. The operation of such prior art vise comprises two steps and is therefore relatively inefficient. Another prior art vise disclosed in the U.S. Pat. No. 4,685,663 comprises two movable jaws coupled respectively with two concentric threaded rods. The two movable jaws are driven separately. Such a vise as described above has a complicated construction and is therefore difficult to operate. In addition, these two prior art vises are defective in design in that they can not locate concentrically the clamped work piece at the time when they are used as a vise with single clamping seat.